Babies Watching People Eat

You may not be surprised to learn that food preference is a social matter. What we choose to eat depends on more than just what tastes good or is healthful. People in different cultures eat different things, and within a culture, what you eat can signal something about who you are.

More surprising is that the sociality of food selection, it turns out, runs deep in human nature. In research published this month in the Proceedings of the National Academy of Sciences, my colleagues and I showed that even 1-year-old babies understand that people’s food preferences depend on their social or cultural group.

Interestingly, we found that babies’ thinking about food preferences isn’t really about food per se. It’s more about the people eating foods, and the relationship between food choice and social groups.

While it’s hard to know what babies think before they can talk, developmental psychologists have long capitalized on the fact that babies’ visual gaze is guided by their interest. Babies tend to look longer at something that is novel or surprising. Do something bizarre the next time you meet a baby, and you’ll notice her looking intently.

Using this method, the psychologists Zoe Liberman, Amanda Woodward, Kathleen Sullivan and I conducted a series of studies. Led by Professor Liberman, we brought more than 200 1-year-olds (and their parents) into a developmental psychology lab, and showed them videos of people visibly expressing like or dislike of foods.

For instance, one group of babies saw a video of a person who ate a food and expressed that she loved it. Next they saw a video of a second person who tried the same food and also loved it. This second event was not terribly surprising to the babies: The two people agreed, after all. Accordingly, the babies did not look for very long at this second video; it was what they expected.

But when the babies saw the second person do something less expected — when this second person instead hated this same food that the first person loved — the babies looked much longer.

In this way, we were able to gauge infants’ patterns of generalization from one person to another. If babies see someone like a food, do they think that other people will like that food, too? And if so, do they think that all people will like the same foods, or just some people?

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We found some surprising patterns. If the two people featured acted as if they were friends, or if they spoke the same language, babies expected that the people would prefer the same foods. But if the two people acted as if they were enemies, or if they spoke two different languages, babies expected that they would prefer two different foods.

It was as if cultural lines were being drawn right in the laboratory. And in the babies’ minds there seemed to be something special about the link between culture and food: When the babies saw people liking and disliking inedible objects, we didn’t observe the same patterns of results.

One thing you may be wondering — and we were, too — is whether this is all about the foods people like. Whether you like grits or kale may depend on cultural identity. But there are some things that are disgusting to all humans, regardless of culture. Do babies intuitively know this?

Indeed, they seem to. When the babies in our studies saw a person act disgusted from eating a food, they expected that a second person would also be disgusted by the same food — regardless of whether or not the two people were in the same social group.

We also discovered something interesting about what babies identify as meaningful cultural differences. Babies from monolingual English-speaking homes saw language as a marker of different cultures; as noted above, if two people spoke two different languages, babies expected that they would prefer two different foods.

In contrast, babies from bilingual homes assumed that even two people who spoke different languages would like to eat the same things. Thus babies have the potential to learn different things about the foods and people around them, depending on their social environments.

Parents of young children may want to take note of our findings. Infants are not just learning to eat the foods they are given; they are also learning by watching adults eat, and figuring out who eats what foods with whom. By introducing babies to social contexts in which adults make healthful food choices, parents may help children learn the cultural norms of healthful eating themselves.

Katherine Kinzler is an associate professor of psychology and human development at Cornell.

A version of this op-ed appears in print on August 21, 2016, on Page SR12 of the New York edition with the headline: Babies Watching People Eat. Today's Paper|Subscribe